A door drive of this type which works both with an absolute value of the path-measuring signal reproducing the door position and with reference points is known from DE 195 22 622 C2. A path-measuring apparatus is associated with the door drive described therein which has a rotary potentiometer which is rotated in accordance with the movement of the door drive. A periodic door position signal in accordance with the door movement is emitted by the potentiometer, with its absolute value, however, not unambiguously indicating the door position, due to the periodicity of the signal. To nevertheless achieve an unambiguous determination of the door position, the maxima and the minima of the potentiometer signal are counted and considered as virtual reference points. The determination of the door position then takes place using the counted reference points and the absolute value of the potentiometer signal following a respective reference point. With this already known door drive, however, a relatively complicated evaluation of the potentiometer signal is required. On the one hand, minima and maxima have to be determined and then counted. In addition, the accuracy of the position determination and, accordingly, the fineness of the control of the door drive tend to be limited, since, beyond the reference points, the exact position determination only takes place using the analog potentiometer signal.
To avoid a reference point determination of this type, it is proposed in WO 02/04775 A1 to provide an absolute value encoder for the sensing of the door position or of the door drive position, with its signal always reproducing the position of the door unambiguously. An inductively operating absolute value encoder is used which reproduces the door position or the door drive position in a door position signal which constantly increases monotonically or constantly decreases monotonically. In addition to this absolute value encoder, an incremental encoder known per se can also be used in accordance with WO 02/04775 A1 which generates corresponding path pulses on a door movement which are then counted to control the door drive accordingly. Provision is made in this process for the control to use either the absolute value signal or the incremental signal for the control of the drive. A switch is made in a time multiplex process between the absolute value signal and the incremental signal. The absolute value signal of the absolute value encoder should in particular be used when the door is at a standstill, whereas the control makes use of the signals of the incremental encoder on movements of the door drive. In this process, however, the usual operating problems with incremental controls can occur such as errors in the signal counting, data amount, etc.
It is therefore the underlying object of the present disclosure to provide an improved door drive control which avoids the disadvantages of the prior art and further develops said prior art in an advantageous manner. An error-free and sensitive control of the door drive should preferably be made possible with a simple signal processing.
This object is solved in accordance with the present disclosure by an apparatus for controlling a door drive comprising: a path-measuring apparatus for the sensing of a door position and/or a door drive position and for the emission of a corresponding door position signal and a control device for the control of the door drive in dependence on an absolute value of the door position signal and at least one reference point, where the path-measuring apparatus is made with at least two channels and includes an absolute value encoder for the emitting of an absolute value signal on a first channel and a reference value encoder for the emitting of a plurality of reference point signals on a second channel; and where the control device distinguishes a respective reference point signal from other reference point signals using the associated absolute value signal and controls the door drive starting from a specific reference point.
In contrast to the already known generic prior art which, the teaching in accordance with the present disclosure makes use of both the absolute value of a door position signal and reference points for the control of the door drive. Further, in one embodiment, the present disclosure dispenses with the complex determination of signal maxima and signal minima and with the counting of such maxima and minima of the absolute door position signal. Instead of determining virtual reference points on the absolute door position signal in a complex manner, the present disclosure provides two separate signals, namely, on the one hand, an absolute door position signal and a preferably digital reference point signal. The path-measuring apparatus is made with at least two channels and includes an absolute value encoder for the emitting of an absolute value signal on a first channel and a reference value encoder for the emitting of a plurality of reference point signals on a second channel. The control device determines the control signal for the control of the door drive from both signals equally. A respective reference point signal is distinguished from other reference point signals using the associated synchronously sensed absolute value signal. The control device then controls the door drive starting from the respectively determined reference point.
Various possibilities result by the combined use of both the absolute value signal and of the separately generated reference point signal. On the one hand, it is possible also to use absolute value signals which, unlike in WO 02/04775 A1, are not constantly monotonic. For the unambiguous determination of the door position, it only has to be ensured that the combination of the respective reference point signal and of the synchronously sensed absolute door position signal is unambiguous. It would be conceivable for this purpose to provide at least two different reference point signal types. On the other hand, it is also possible to work with only one single reference point signal type, i.e. the reference point signal which is the same per se is always generated on the sweeping over of the different reference points when the absolute value encoder emits an unambiguously discrete absolute value signal over the total travel path. In comparison with DE 195 22 622 C2, it is possible to dispense with the painstaking signal evaluation, i.e. the determination of maxima and minima and their counting, by the combination of an absolute value signal and a separate reference point signal.
In a further development of the present disclosure, the path-measuring device is made with three channels. In addition to the absolute value signal and to the reference point signal, path pulses are generated by an incremental encoder on a third channel on a movement of the door or of the door drive. The control device counts these incremental path pulses starting from a specific reference point and controls the door drive in dependence on the number of counted path pulses. By the use of these three path-measuring signals, i.e. of an absolute value signal, a reference point signal and of incremental path pulses, in combination with one another, the advantages of the individual control systems can be maintained, but the disadvantages can be eliminated. A coarse control so-to-say takes place using the absolute value signal, i.e. the majority of reference points can be distinguished from one another in a simple manner. In addition, the usual problems of reference point controls and incremental controls on a power failure or an uncoupled manual operation of the door no longer play a role. The control always knows in which position the door is located, at least roughly. On the other hand, a fine control is made possible by the path pulses of the incremental encoder which would never be achievable alone with the always limited resolution of an absolute value signal. In this process, the processing of the signals of the incremental encoder is simplified by making use of reference points.
In accordance with a particularly advantageous embodiment of the present disclosure, the absolute value encoder and the reference point encoder are combined in a single sensor. A two-channel path sensor can in particular be provided in which the said absolute value encoder and the reference point encoder are integrated. In addition to this two-channel path sensor, a path signal encoder can be provided separately which is incremental per se.
In a further development of the present disclosure, a potentiometer can be provided as the absolute value encoder which preferably emits an unambiguously discrete absolute value signal over the whole travel path of the door and/or of the door drive. A voltage switch can be provided as the reference point encoder. The designing of the absolute value encoder as a potentiometer and of the reference point encoder as a voltage switch makes it possible in a simple manner to integrate these two components in one single sensor.
The path sensor advantageously has a signal encoder element which is movable in accordance with the door movement and/or the door drive movement and by which both the absolute value encoder and the reference point encoder can be actuated. The signal encoder element can in particular carry two pick-ups, of which the one actuates a potentiometer circuit and the other actuates a voltage switch.
In an advantageous further development of the present disclosure, both the potentiometer circuit and the circuit forming the voltage switch are arranged in the form of concentric circles on a substrate relative to which the said signal encoder element is rotatably supported. Said signal encoder element is rotated over the substrate in accordance with the door movement or door drive movement and in this process actuates both the potentiometer circuit which makes the absolute value signal available and the circuit which forms the voltage switch and emits the reference points for the corresponding door movement.